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27 Cards in this Set
- Front
- Back
Definition of magnification |
the number of times an image appears larger compared to the actual size of the object |
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What formula is used to calculate Magnification? |
The triangle is Observed size/ Actual size X Magnification |
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Convert: Centimeter (cm) Millimeter (mm) to Micrometer (um) to Nanometer (nm) |
Centimeter X 1000 to Milimeter X 1000 to Micrometer X 1000 to Nanometer |
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Definition of resolution |
the ability to distinguish between two different points |
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Best resolution of a light microscope |
0.2 micrometres |
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Best magnification of a light microscope |
x1500 |
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What are Light microscope mainly used to look at? |
To look at whole cells or tissues |
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How does a light microscope work? |
> They use light and several lenses in order to magnify.> Specimens are illuminated with light which is focused using glass lenses |
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Advantages of a light microscope |
> Cheap > Easy to use > Can examine living things |
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Disadvantages of a light microscope |
> Specimens have to be small, thin and transparent > Have a low resolution due to light |
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How does a confocal scanning microscope work? |
> They use laser lights to scan a specimen thats usually tagged with fluorescent dyes. > The laser beam which is focused through a lens is aimed at a beam splitter > This splits the beam and some of the light to the specimen > When the laser hits the dyes it causes them to give off fluorescent light >This light is then focused through a pinhole onto a detector which is hooked up to a computer, which generates an image. overall use laser light to scan an object point by point and assemble, by computer, the pixel information into one image |
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What does a pinhole for laser scanning microscope do? |
The pinhole means that any out-of-focus light is blocked, so these microscopes produce a much clearer image |
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Advantages of a confocal scanning microscope |
> Builds a clean 3d image > Can look at objects at different depths in thick specimens > Images are high resolution |
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Disadvantages of a confocal scanning microscope |
> Quite big > Doesn't always show full sample |
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Best resolution of a confocal scanning microscope |
20 nanometres |
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Best magnification of a confocal scanning microscope |
x1500 |
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How does a TEM Microscope work? |
> They use elctromagnets to focus a beam of electrons which is then transmitted through the specimen to produce a 2D image. > Denser parts of the specimen absorb more elections, which makes them look darker on the image. |
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Advantages of TEM |
> Can look at small organelles > High resolution |
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Disadvantages of TEM |
> Can only be used on thin specimens > Angles at which the specimen is cut can affect how they appear > Specimen are dead as they must be viewed in a vacuum |
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Best resolution of TEM |
0.0002 micrometres or 0.2 nm |
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Best magnification of TEM |
more than 1,000,000 |
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How does a SEM work? |
They scan a beam of electrons across the specimens. This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image. |
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Advantages of a SEM |
produces a 3D image |
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Disadvantage of SEM |
> Have a lower resolution than TEMs > Specimens are dead as they must be viewed in a vacuum > Only shows the surface of cells |
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Best resolution of SEM |
0.002 micrometres |
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Best magnification of SEM |
less than 500,000 |
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Similarities of SEM & TEM |
> Both are large and very expensive > Need a great deal of skills and trainning to use |